This invention relates to Die Bonder Wafermap operations and, more particularly, to recovery in case of loss of wafermap coordinate data.
Semiconductor manufacturing includes the process of moving semiconductor substrate dies from a wafer table to a lead frame after they have been cut from a silicon wafer of substrate material. A silicon wafer first is placed on an adhesive surface and is cut into rectangular dies. After cutting, the adhesive surface is placed on a wafer table of a die bonder apparatus. The die bonder deposits an adhesive on the lead frame, removes a cut die from the adhesive surface, and places it on the lead frame on the deposited adhesive. The silicon wafer from which the dies are cut is round, such that some dies are not fully rectangular. These nonrectangular dies will be left on the adhesive surface and discarded.
If the process of removing dies from a silicon wafer is automated, the position of the silicon wafer and dies must be known or estimated, to allow a robot arm to manipulate the wafer and dies. Nevertheless, the position of the silicon wafer with respect to the known coordinates of the adhesive surface may randomly change during the die cutting operation. When such random changes occur, no die may be present at some locations in which a die is expected. This condition may result in unnecessary wafer table movements to locate the cut dies.
A wafer may have dies of varying quality such as top grade dies, second grade but usable dies, and bad dies. The dies of like grade are given a given bin number and dies of the same bin are picked by the die bonder.
In the prior art in the case of loss of wafermap coordinate data, the operator needs to count the number of dies to skip by counting the picked dies in the wafer. In the case of small dies, counting is not possible.
In accordance with one embodiment of the present invention, a method for automatic recovery for die bonder wafer table wafermap operation is provided.